A rotary actuator of an add-on type, which is used as a drive device for driving a shift-by-wire system of a vehicle transmission, has been known. This rotary actuator is fixed to an outer wall of a transmission case and is connected to a control rod of a shift range change mechanism through a connection hole formed in the transmission case. The shift range change mechanism changes a shift range of the transmission according to a rotational position of the control rod. When the rotational position of the control rod is a corresponding position that corresponds to a parking range, the shift range change mechanism locks rotation of the output shaft of the transmission.
In the shift-by-wire system that is constructed in the above described manner, when the rotary actuator becomes inoperable due to, for example, a failure of the rotary actuator in a state where the shift range is held in the parking range, the lock of the output shaft of the transmission cannot be released by the shift range change mechanism. In order to move the vehicle under this situation, it is necessary to lift drive wheels of the vehicle. In order to alleviate the above disadvantage, the shift-by-wire system disclosed in the patent literature 1 has an auxiliary change lever that is manually operable by an operator to change the shift range by rotating the control rod.
Normally, the auxiliary change lever of the above type is connected to the control rod placed in an inside of the transmission case through a cable. In such a case, a hole for inserting the cable needs to be formed at the transmission case, and a gap between this hole and the cable needs to be sealed. Therefore, in a case of newly installing the shift-by-wire system, it is necessary to develop a dedicated transmission, or to make significant improvements to the preexisting transmission, resulting in high costs. Therefore, the advantage of easy installation of the shift-by-wire system to the vehicle through use of the rotary actuator of the add-on type could be deteriorated.